Broken local symmetry in paraelectric BaTiO3 proved by second harmonic generation

Precursor dynamics of a cubic to tetragonal ferroelectric phase transition in BaTiO3 is studied by the accurate measurement of the second harmonic generation (SHG) integral intensities. A finite signal holds for the SHG integrated intensity above the ferroelectric Curie temperature T(c)=403  K. Abov...

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Veröffentlicht in:Physical review letters 2012-06, Vol.108 (24), p.247601-247601
Hauptverfasser: Pugachev, A M, Kovalevskii, V I, Surovtsev, N V, Kojima, S, Prosandeev, S A, Raevski, I P, Raevskaya, S I
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Sprache:eng
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Zusammenfassung:Precursor dynamics of a cubic to tetragonal ferroelectric phase transition in BaTiO3 is studied by the accurate measurement of the second harmonic generation (SHG) integral intensities. A finite signal holds for the SHG integrated intensity above the ferroelectric Curie temperature T(c)=403  K. Above the Burn's temperature T(d)≈580  K, the power law with the exponent γ=1 shows normal SHG nature originating from the hyper-Raman scattering by dynamical polar excitations, while, below T(d), a SHG signal from polar nanoregions becomes dominant with the larger exponent γ=2. Such a crossover of the power law exponent near T(d) is discussed on the basis of the effective Hamiltonian method and Monte Carlo simulation.
ISSN:1079-7114
DOI:10.1103/PhysRevLett.108.247601